cartner on environmental heat stress

Environmental(HEAT)

BCC 2012. Michaela Cartner

MdS….Sahara Ultramarathon

Heat Production

• Humans are furnaces

• 1.1’ C hourly rise

• x20 with exercise

• 42’ C Core temp in trained athletes

Environmental Heat Transfer

4 Mechanisms

Environmental Heat Transfer: CONDUCTION

The transfer of heat by direct physical contact

Environmental Heat Transfer: CONVECTION

The transfer of heat to air and water molecules.

Environmental Heat Transfer: RADIATION

The transfer of heat via EMG waves. Up to 300kCl /hr

Environmental Heat Transfer: EVAPORATION

Dominant method of cooling. 1ml of sweat will cool the body by 0.58kcal *(BMR 100kcal/hr :. 200mls sweat)

PATHOPHYSIOLOGY

Predisposing factors for heat illness

Classic

Classic

Classic

Heat Strain Indexes

• Meterological– The wet bulb globe

temperature index.– WBGT= 0.7Tw +

0.2Tg +Ta

– In use by the Military and athletes

• “ I saved a gram by cutting the tags off my wind pants and an inch off the end of each drawstring” irunfar.com (Bryon Powell)

Heat Illnesses

Davidatmds2012.weebly.com

“Once the brain started to ignore those repetitive pain signals, comfort levels generally became bearable” Perratt.me.uk

• The Doc Trotters (52 members, 6000 painkillers and 150L Disinfectant)• Feet preparations include vet supplies/formalin/picric acid/ benzoin /alcohol /henna

/curry Runningsahara.com/training/feet-the-ultimate-training–and-preparation

Heat Oedema

Heat Exhaustion

1 Saline drip = 2hr time penalty2 Saline drips = Disqualified

Heat Exhaustion•Water depletion •Salt depletion

“ Voluntary Dehydration”2/3 of net water loss replaced

•Treat with Saline if orthostatic•Replace with free water <2mOsm/hr.

Oral rehydration should include cool fluids with 7% carbohydrateAbsorbtion 30% FASTER THAN FREE WATER

Heat Stroke

“ While I was coherent, I saw some amazing sights.…

Runners passing out at the top of the dunes and tumbling to the base

- one elite runner broke his leg…”

Perratt.me.uk Jackson Griffith

Heat Stroke

• Rhabdomyolysis + altered LFTs

• Renal failure

• Sweating in 50%• Hypoglycaemia• Coagulopathy

• Hyponatraemia

• CNS- seizures in 75%

Paul Williams, Extreme Ironer MdS 2012

Heat Stroke- Treatment

• It does not take long either to boil an egg or cook neurons.

D. Hamilton

The Immediate Treatment of Heatstroke Anaesthesia 1976; 31:270-272

Heat Stroke…Treatment

Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507

Heat Stroke…Treatment

Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507

ADF Health Vol 11 2010 pp 9-12

Heat Stroke…Treatment

• Adjuncts– ICE PACKS– Cooling blankets

– Lavage

– CPB

- BZD

- Discontinue cooling when 39’C

• Fluids– Relative not absolute – Evidence of RHF

Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507

The End

Thank you

Samwestonsimonds.com